Immune responses associated with protection induced by chemoattenuated PfSPZ vaccine in malaria-naive Europeans.

Vaccination of malaria-naive volunteers with a high dose of Plasmodium falciparum sporozoites chemoattenuated by chloroquine (CQ) (PfSPZ-CVac [CQ]) has previously demonstrated full protection against controlled human malaria infection (CHMI). However, lower doses of PfSPZ-CVac [CQ] resulted in incomplete protection. This provides the opportunity to understand the immune mechanisms needed for better vaccine-induced protection by comparing individuals who were protected with those not protected. Using mass cytometry, we characterized immune cell composition and responses of malaria-naive European volunteers who received either lower doses of PfSPZ-CVac [CQ], resulting in 50% protection irrespective of the dose, or a placebo vaccination, with everyone becoming infected following CHMI. Clusters of CD4+ and γδ T cells associated with protection were identified, consistent with their known role in malaria immunity. Additionally, EMRA CD8+ T cells and CD56+CD8+ T cell clusters were associated with protection. In a cohort from a malaria-endemic area in Gabon, these CD8+ T cell clusters were also associated with parasitemia control in individuals with lifelong exposure to malaria. Upon stimulation with P. falciparum-infected erythrocytes, CD4+, γδ, and EMRA CD8+ T cells produced IFN-γ and/or TNF, indicating their ability to mediate responses that eliminate malaria parasites.

Assessing the Incidence of Snakebites in Rural Gabon-A Community-Based, Cross-Sectional Pilot Survey.

Snakebite envenoming (SBE) is a neglected tropical disease (NTD). Community-based studies from sub-Saharan Africa are urgently required as data on the incidence are scarce. This study aimed to determine the lifetime prevalence of snakebites in rural Gabon by preparing the conduct of a larger regional survey. A cross-sectional community-based epidemiological survey in Sindara, Ngounie province, was conducted. Households were interviewed about the history of snakebites of household members to calculate lifetime prevalence. In addition, the average annual incidence rate per 100,000 over the last 5 years was calculated. A total of 771 inhabitants were enrolled, of which 5 (0.65%; 95% confidence interval (95% CI: 0.2-1.5%)) were victims of snakebites. Over the past 5 years, annual incidence was 77 bites per 100,000 (95% CI: 0-620). This study provides a first rough estimate of the incidence of SBE from rural central Gabon, demonstrating the importance of this NTD. Key Contribution: The estimated annual incidence of snakebites found was 77 per 100,000. Snakebites occurred mainly during agricultural activities.

Gut microbiota in vaccine naïve Gabonese children with rotavirus A gastroenteritis.

Background: While the gut microbiome modulates the pathogenesis of enteric viruses, how infections caused by rotavirus A (RVA), with or without diarrhoea, alter the gut microbiota has been sparsely studied. Methods: From a cohort of 224 vaccine naïve Gabonese children with and without diarrhoea (n = 177 and n = 67, respectively), 48 stool samples were analysed: (i) RVA with diarrhoea (n = 12); (ii) RVA without diarrhoea (n = 12); (iii) diarrhoea without RVA (n = 12); (iv) healthy controls without diarrhoea and RVA (n = 12). The 16S rRNA metabarcoding using Oxford Nanopore sequencing data was analysed for taxonomic composition, abundance, alpha and beta diversity, and metabolic pathways. Findings: Alpha diversity showed that children with acute diarrhoea (with and without RVA infection), and children with acute diarrhoea without RVA had low microbial diversity compared to healthy children (p = 0.001 and p = 0.006, respectively). No significant differences observed when comparing children with RVA with or without diarrhoea. Beta diversity revealed high microbial heterogeneity in children without diarrhoea. Proteobacteria (68%) and Firmicutes (69%) were most common in the diarrhoea and non-diarrhoea groups, respectively. Proteobacteria (53%) were most common in children without RVA, while Firmicutes (55%) were most common with RVA. At the genus level, Escherichia (21%), Klebsiella (10%) and Salmonella (4%) were abundant in children with diarrhoea, while Blautia (11%), Clostridium (8%), Lachnoclostridium (6%) and Ruminococcus (5%) were abundant in children without diarrhoea. Metabolites involved in amino acid, carbohydrate, lipid, nucleotide, and vitamin metabolism were quantitatively altered. Interpretation: Although host physiology dictates the intestinal milieu, diarrhoea per se can alter a balanced gut microbiota, whereas infectious diarrhoea disrupts the gut microbiome and reduces its diversity.

A randomized assessors-blind clinical trial to evaluate the safety and the efficacy of albendazole alone and in combination with mebendazole or pyrantel for the treatment of Trichuris trichiura infection in school-aged children in Lambaréné and surroundings.

Helminthiasis remains a public health issue in endemic areas. Various drugs have been proposed to improve efficacy against helminths. The study aimed to assess the safety and efficacy of three different anthelmintic combinations to treat Trichuris trichiura infections. We conducted a randomized assessors-blind clinical trial involving children aged 2-17 years with T. trichiura. Participants were randomly assigned to one of three treatment arms. On the first and third days, all participants got albendazole 400 mg, and on the second day, albendazole (arm A), mebendazole 500 mg (arm B), or pyrantel 125 mg/kg (arm C). We assessed treatment efficacy using the cure rate (CR) and egg reduction rate (ERR) at 3 and 6 weeks post-treatment. At 3 weeks post-treatment, ERR and CR were highest in study arm A [ERR = 94%, 95% confidence interval (CI): 92-95; CR = 71%; 95% CI: 58-81] compared to the B and C arms. Decrease in ERR was significant only for arm B versus arm A (P-value <0.001); decrease in ERR was significant for arms B and C (P-value <0.001). No statistical difference was observed in CR when comparing arms A and B (P-value =1.00) and C (P-value =0.27). At 6 weeks, a decrease in ERR was observed in three arms, significant only for arm C, 81% (95% CI: 78-83). A significant increase in egg counts was observed between 3 and 6 weeks post-treatment. All treatments were safe with mild adverse events. Albendazole 400 mg/day (arm A) showed the highest efficacy against trichuriasis. Nonetheless, this treatment regimen was able to cure half of the treated individuals highlighting concerns about controlling the transmission of T. trichiura.CLINICAL TRIALRegistered at ClinicalTrials.gov (NCT04326868).

A severe case of Plasmodium falciparum malaria in a traveler returning from Kazakhstan, a malaria-free country.

Following a 2-week trip to Kazakhstan, a 42-year-old woman presented at the emergency department in Germany with fever, headache, nausea, and neurological symptoms. An infection with Plasmodium falciparum was rapidly diagnosed. The patient was immediately treated with intravenous artesunate and transferred to an intensive care unit. The initial parasite density was as high as 30% infected erythrocytes with 845,880 parasites/µL. Since Kazakhstan was declared malaria-free in 2012, molecular testing for Plasmodium has been initiated to identify a possible origin. Genotyping of the msp-1 gene and microsatellite markers showed that the parasites are of African origin, with two different alleles indicating a polyclonal infection. After a hospitalization of 10 days, the patient was discharged in good health. Overall, our results emphasize that malaria must be on the list of differential diagnoses for patients with fever of unknown origin, even if they come from countries where malaria does not commonly occur.

Dynamics of Plasmodium species and genotype diversity in adults with asymptomatic infection in Gabon.

OBJECTIVES: We investigated the diversity and dynamics of Plasmodium infection in serially collected samples from asymptomatic participants of a clinical trial assessing the efficacy and safety of ivermectin in Gabon. We checked whether the baseline sample reflected the P. falciparum genotype and Plasmodium species diversity seen over 7 days of follow-up. METHODS: Blood samples were collected at inclusion, every 8 hours until hour 72, daily until day 7, and on day 14. Plasmodium species was determined by qPCR and pfmsp1 length polymorphism was assessed for P. falciparum genotyping. RESULTS: In 17/48 (35%) individuals, all pfmsp1 genotypes identified during the assessed period were detected at baseline; in 31/48 (65%), new genotypes were found during follow-up. Additional sampling at hour 24 allowed the identification of all genotypes seen over 7 days in 50% of the individuals. Ivermectin did not impact the genotype dynamics. Mixed Plasmodium spp. infections were detected in 28/49 (57%) individuals at baseline, and detection of non-falciparum infections during follow-up varied. CONCLUSIONS: Our results reveal complex intra-host dynamics of P. falciparum genotypes and Plasmodium species and underscore the importance of serial sampling in clinical trials for antimalarial drugs with asymptomatically P. falciparum-infected individuals. This might allow a more accurate identification of genotypes in multiple infections, impacting the assessment of drug efficacy.

Safety and immunogenicity of the co-administered Na-APR-1 and Na-GST-1 hookworm vaccines in school-aged children in Gabon: a randomised, controlled, observer-blind, phase 1, dose-escalation trial.

BACKGROUND: A human hookworm vaccine is being developed to protect children against iron deficiency and anaemia associated with chronic infection with hookworms. Necator americanus aspartic protease-1 (Na-APR-1) and N americanus glutathione S-transferase-1 (Na-GST-1) are components of the blood digestion pathway critical to hookworm survival in the host. Recombinant Na-GST-1 and catalytically inactive Na-APR-1 (Na-APR-1[M74]) adsorbed to Alhydrogel were safe and immunogenic when delivered separately or co-administered to adults in phase 1 trials in non-endemic and endemic areas. We aimed to investigate the safety and immunogenicity of these antigens in healthy children in a hookworm-endemic area. METHODS: This was a randomised, controlled, observer-blind, phase 1, dose-escalation trial, conducted in a clinical research centre, in 60 children aged six to ten years in Lambaréné, a hookworm-endemic region of Gabon. Healthy children (determined by clinical examination and safety laboratory testing) were randomised 4:1 to receive co-administered Na-GST-1 on Alhydrogel plus Na-APR-1(M74) on Alhydrogel and glucopyranosyl lipid A in aqueous formulation (GLA-AF), or co-administered ENGERIX-B hepatitis B vaccine (HBV) and saline placebo, injected into the deltoid of each arm. Allocation to vaccine groups was observer-masked. In each vaccine group, children were randomised 1:1 to receive intramuscular injections into each deltoid on two vaccine schedules, one at months 0, 2, and 4 or at months 0, 2, and 6. 10 µg, 30 µg, and 100 µg of each antigen were administered in the first, second, and third cohorts, respectively. The intention-to-treat population was used for safety analyses; while for immunogenicity analyses, the per-protocol population was used (children who received all scheduled vaccinations). The primary outcome was to evaluate the vaccines' safety and reactogenicity in healthy children aged between six and ten years. The secondary outcome was to measure antigen-specific serum IgG antibody levels at pre-vaccination and post-vaccination timepoints by qualified ELISAs. The trial is registered with ClinicalTrials.gov, NCT02839161, and is completed. FINDINGS: Between Jan 23 and Oct 3, 2017, 137 children were screened, of whom 76 were eligible for this trial. 60 children were recruited, and allocated to either 10 µg of the co-administered antigens (n=8 for each injection schedule), 30 µg (n=8 for each schedule), 100 µg (n=8 for each schedule), or HBV and placebo (n=6 for each schedule) in three sequential cohorts. Co-administration of the vaccines was well tolerated; the most frequent solicited adverse events were mild-to-moderate injection-site pain, observed in up to 12 (75%) of 16 participants per vaccine group, and mild headache (12 [25%] of 48) and fever (11 [23%] of 48). No vaccine-related serious adverse events were observed. Significant anti-Na-APR-1(M74) and anti-Na-GST-1 IgG levels were induced in a dose-dependent manner, with peaks seen 14 days after the third vaccinations, regardless of dose (for Na-APR-1[M74], geometric mean levels [GML]=2295·97 arbitrary units [AU] and 726·89 AU, while for Na-GST-1, GMLs=331·2 AU and 21·4 AU for the month 0, 2, and 6 and month 0, 2, and 4 schedules, respectively). The month 0, 2, and 6 schedule induced significantly higher IgG responses to both antigens (p=0·01 and p=0·04 for Na-APR-1[M74] and Na-GST-1, respectively). INTERPRETATION: Co-administration of recombinant Na-APR-1(M74) and Na-GST-1 to school-aged Gabonese children was well tolerated and induced significant IgG responses. These results justify further evaluation of this antigen combination in proof-of-concept controlled-infection and efficacy studies in hookworm-endemic areas. FUNDING: European Union Seventh Framework Programme.

Analysis of diagnostic test outcomes in a large loiasis cohort from an endemic region: Serological tests are often false negative in hyper-microfilaremic infections.

BACKGROUND: The parasitic disease loiasis is associated with significant morbidity and mortality. Individuals with hyper-microfilaremia (greater than 20,000 microfilariae per mL of blood) may suffer from serious treatment-related or spontaneous adverse events. Diagnosing loiasis remains complex and primarily relies on direct parasite detection. In this study, we analyzed the performance of various diagnostic tests and the influence of parasitological and clinical factors on test outcomes in samples from individuals living in an endemic region. METHODS: Data and samples were collected from rural Gabon. Loiasis was defined as either detectable microfilaremia, or a positive history of eyeworm as assessed by the RAPLOA questionnaire. Diagnostic testing included a quantitative PCR (qPCR) for detection of Loa loa DNA in blood samples, an in-house crude L. loa antigen IgG ELISA, and a rapid test for antibodies against the Ll-SXP-1 antigen (RDT). Sensitivity and specificity were determined for each test and factors potentially influencing outcomes were evaluated in an exploratory analysis. RESULTS: ELISA, RDT and qPCR results were available for 99.8%, 78.5%, and 100% of the 1,232 participants, respectively. The ELISA and RDT had only modest diagnostic accuracy. qPCR was specific for L. loa microfilaremia and Cycle threshold values correlated with microfilarial density. Anti-L. loa IgG levels were highest in occult loiasis, and antibody levels correlated inversely with L. loa microfilarial density as did RDT line intensities. Only 84.6% and 16.7% of hyper-microfilaremic individuals tested positive by ELISA (11/13) and RDT (2/12), respectively. CONCLUSION: None of the tests demonstrated high sensitivity and specificity for loiasis. Indirect diagnostic assays were characterized by low specificity. Additionally, hyper-microfilaremic individuals often tested negative by RDT and ELISA, indicating that these tests are not suitable for individual case management in endemic populations.

Markers of prolonged hospitalisation in severe dengue.

BACKGROUND: Dengue is one of the most common diseases in the tropics and subtropics. Whilst mortality is a rare event when adequate supportive care can be provided, a large number of patients get hospitalised with dengue every year that places a heavy burden on local health systems. A better understanding of the support required at the time of hospitalisation is therefore of critical importance for healthcare planning, especially when resources are limited during major outbreaks. METHODS: Here we performed a retrospective analysis of clinical data from over 1500 individuals hospitalised with dengue in Vietnam between 2017 and 2019. Using a broad panel of potential biomarkers, we sought to evaluate robust predictors of prolonged hospitalisation periods. RESULTS: Our analyses revealed a lead-time bias, whereby early admission to hospital correlates with longer hospital stays - irrespective of disease severity. Importantly, taking into account the symptom duration prior to hospitalisation significantly affects observed associations between hospitalisation length and previously reported risk markers of prolonged stays, which themselves showed marked inter-annual variations. Once corrected for symptom duration, age, temperature at admission and elevated neutrophil-to-lymphocyte ratio were found predictive of longer hospitalisation periods. CONCLUSION: This study demonstrates that the time since dengue symptom onset is one of the most significant predictors for the length of hospital stays, independent of the assigned severity score. Pre-hospital symptom durations need to be accounted for to evaluate clinically relevant biomarkers of dengue hospitalisation trajectories.

Emergence of Novel Norovirus GII.4 Variant.

We detected a novel GII.4 variant with an amino acid insertion at the start of epitope A in viral protein 1 of noroviruses from the United States, Gabon, South Africa, and the United Kingdom collected during 2017-2022. Early identification of GII.4 variants is crucial for assessing pandemic potential and informing vaccine development.

Mucosal response of inactivated and recombinant COVID-19 vaccines in Congolese individuals.

BACKGROUND: The efficacy of immunization against an airborne pathogen depends in part on its ability to induce antibodies at the major entry site of the virus, the mucosa. Recent studies have revealed that mucosal immunity is poorly activated after vaccination with messenger RNA vaccines, thus failing in blocking virus acquisition upon its site of initial exposure. Little information is available about the induction of mucosal immunity by inactivated and recombinant coronavirus disease 2019 (COVID-19) vaccines. This study aims to investigate this topic. METHODS: Saliva and plasma samples from 440 healthy Congolese were collected including (1) fully vaccinated 2 month postvaccination with either an inactivated or a recombinant COVID-19 vaccine and (2) nonvaccinated control group. Total anti-severe acute respiratory syndrome coronavirus 2 receptor-binding domain IgG and IgA antibodies were assessed using in-house enzyme-linked immunosorbent assays for both specimens. FINDINGS: Altogether, the positivity of IgG was significantly higher in plasma than in saliva samples both in vaccinated and nonvaccinated control groups. Inversely, IgA positivity was slightly higher in saliva than in plasma of vaccinated group. The overall IgG and IgA levels were respectively over 103 and 14 times lower in saliva than in plasma samples. We found a strong positive correlation between IgG in saliva and plasma also between IgA in both specimens (r = .70 for IgG and r = .52 for IgA). Interestingly, contrary to IgG, the level of salivary IgA was not different between seropositive control group and seropositive vaccinated group. No significant difference was observed between recombinant and inactivated COVID-19 vaccines in total IgG and IgA antibody concentration release 2 months postvaccination both in plasma and saliva. CONCLUSION: Inactivated and recombinant COVID-19 vaccines in use in the Republic of Congo poorly activated mucosal IgA-mediated antibody response 2 months postvaccination.

Anopheles gambiae s.s. resistance to pyrethroids and DDT in semi-urban and rural areas of the Moyen-Ogooué Province, Gabon.

BACKGROUND: Pyrethroids are the main insecticides used in vector control for malaria. However, their extensive use in the impregnation of long-lasting insecticidal nets (LLINs) and indoor residual spraying has led to the development of resistance, threatening its success as a tool for malaria control. Baseline data prior to large scale distribution of LLINs are important for the implementation of efficient strategies. However, no data on the susceptibility of malaria vectors is available in the Moyen-Ogooué Province in Gabon. The aim of this study was to assess the susceptibility to pyrethroids and organochlorides of malaria vectors from a semi-urban and rural areas of the province and to determine the frequency of insecticide resistance genes. METHODS: Larvae were collected from breeding sites in Lambaréné and Zilé and reared to adults. Three to five-day old female Anopheles gambiae sensu lato mosquitoes were used in cone tube assays following the WHO susceptibility tests protocol for adult mosquitoes. A subsample was molecularly identified using the SINE200 protocol and the frequency of Vgsc-1014 F and - 1014 S mutations were determined. RESULTS: Anopheles gambiae sensu stricto (s.s.) was the sole species present in both Lambaréné and Zilé. Mosquito populations from the two areas were resistant to pyrethroids and organochlorides. Resistance was more pronounced for permethrin and DDT with mortality lower than 7% for both insecticides in the two study areas. Mosquitoes were statistically more resistant (P < 0.0001) to deltamethrin in Lambaréné (51%) compared to Zilé (76%). All the mosquitoes tested were heterozygous or homozygous for the knockdown resistance (Kdr) mutations Vgsc-L1014F and Vgsc-L1014S with a higher proportion of Vgsc-L1014F homozygous in Lambaréné (76.7%) compared to Zilé (57.1%). CONCLUSION: This study provides evidence of widespread resistance to pyrethroids in An. gambiae s.s., the main malaria vector in the Moyen-Ogooué Province. Further investigation of the mechanisms underlining the resistance of An. gambiae s.s. to pyrethroids is needed to implement appropriate insecticide resistance management strategies.

Tübingen model study: large-scale introduction of rapid antigen testing in the population and the viral dynamics of SARS-CoV-2.

Despite of contact restrictions, population mobility remains the main reason for the spread of SARS-CoV-2. The state of Baden-Württemberg (BW), Germany, approved a model study in Tübingen (TÜMOD) to evaluate how mandatory rapid diagnostic tests (RDT) could reduce transmission. Between 16 March and 24 April 2021, approximately 165,000 residents and visitors to the city were screened for SARS CoV-2 infection using Abbott Panbio™ COVID-19 Antigen rapid test device. We assessed incidences and recorded epidemiological characteristics in a subset of 4,118 participants recruited at three of the nine testing stations. PCR tests were performed in RDT-positives to determine the positive predictive value (PPV), and circulating variants of SARS-CoV-2 were identified by whole-genome sequencing. 2,282 RDT-negative samples were tested by pooled PCR to calculate the false negative rate (FNR). Viral load was compared between variants. 116 (3%) participants were positive by RDT, and of these, 57 (49%) were positive by PCR, 55 (47%) were negative. This resulted in a PPV of 51%. Of the 57 positives, 52 SARS-CoV-2 genomes were successfully sequenced. Of these, 50 belonged to the B.1.1.7 lineage, which had a high viral load (average Ct = 19). Of the 2,282 RDT negatives tested, all were PCR negative (FNR 0%). At the end of TÜMOD, the incidence in Tübingen, which was initially lower, had reached the incidence in the state of BW. While it is difficult to assess the impact of TÜMOD on incidence independent of confounding factors, further studies are needed to identify the effect of close-meshed testing on infection rates.

Efficacy and safety of ivermectin for the treatment of Plasmodium falciparum infections in asymptomatic male and female Gabonese adults - a pilot randomized, double-blind, placebo-controlled single-centre phase Ib/IIa clinical trial.

BACKGROUND: Ivermectin's mosquitocidal effect and in vitro activity against Plasmodium falciparum asexual stages are known. Its in vivo blood-schizonticidal efficacy is unknown. Ivermectin's tolerability and efficacy against P. falciparum infections in Gabonese adults were assessed. METHODS: The study consisted of a multiple dose stage and a randomized, double-blind, placebo-controlled stage. Adults with asymptomatic P. falciparum parasitaemia (200-5000 parasites/µl) were enrolled. First, three groups of five participants received 200 µg/kg ivermectin once daily for one, two, and three days, respectively, and then 34 participants were randomized to 300 µg/kg ivermectin or placebo once daily for 3 days. Primary efficacy outcome was time to 90% parasite reduction. Primary safety outcomes were drug-related serious and severe adverse events (Trial registration: PACTR201908520097051). FINDINGS: Between June 2019 and October 2020, 49 participants were enrolled. Out of the 34 randomized participants, 29 (85%) completed the trial as per protocol. No severe or serious adverse events were observed. The median time to 90% parasite reduction was 24.1 vs. 32.0 h in the ivermectin and placebo groups, respectively (HR 1.38 [95% CI 0.64 to 2.97]). INTERPRETATION: Ivermectin was well tolerated in doses up to 300 µg/kg once daily for three days and asymptomatic P. falciparum asexual parasitaemia was reduced similarly with this dose of ivermectin compared to placebo. Further studies are needed to evaluate plasmodicidal effect of ivermectin at higher doses and in larger samples. FUNDING: This study was funded by the Centre de Recherches Médicales de Lambaréné and the Centre for Tropical Medicine of the Bernhard Nocht Institute for Tropical Medicine.

Species identification and drug susceptibility testing of non-tuberculous mycobacteria by Line Probe Assay in Lambaréné, Gabon-a cross-sectional study.

BACKGROUND: Non-tuberculous mycobacteria (NTM) are a group of bacteria that cause rare lung infections and are increasingly recognized as causative agents of opportunistic and device-associated infections in humans. In Gabon, there is a lack of data on NTM species identification and drug susceptibility. The aim of this study was to identify the frequency of NTM species and their genotypic susceptibility pattern to commonly used antibiotics for NTM infections in Gabon. METHODS: A cross-sectional study was conducted at the CERMEL TB laboratory from January 2020 to December 2022, NTM subspecies identification and drug susceptibility testing to macrolides and aminoglycosides were performed using the genotype NTM-DR kit. RESULTS: The study found that out of 524 culture-positive specimens, 146 (28%) were NTM, with the predominant group being Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MABC). All MAC isolates were fully susceptible to macrolides and aminoglycosides, while five MABC isolates carried mutations indicative of reduced susceptibility to macrolide and aminoglycoside drugs. CONCLUSIONS: These findings suggest that clinicians may use macrolides and aminoglycosides to manage NTM infections caused by MAC, but further investigation is required to determine MABC drug susceptibility.

Time to establish an international vaccine candidate pool for potential highly infectious respiratory disease: a community's view.

In counteracting highly infectious and disruptive respiratory diseases such as COVID-19, vaccination remains the primary and safest way to prevent disease, reduce the severity of illness, and save lives. Unfortunately, vaccination is often not the first intervention deployed for a new pandemic, as it takes time to develop and test vaccines, and confirmation of safety requires a period of observation after vaccination to detect potential late-onset vaccine-associated adverse events. In the meantime, nonpharmacologic public health interventions such as mask-wearing and social distancing can provide some degree of protection. As climate change, with its environmental impacts on pathogen evolution and international mobility continue to rise, highly infectious respiratory diseases will likely emerge more frequently and their impact is expected to be substantial. How quickly a safe and efficacious vaccine can be deployed against rising infectious respiratory diseases may be the most important challenge that humanity will face in the near future. While some organizations are engaged in addressing the World Health Organization's "blueprint for priority diseases", the lack of worldwide preparedness, and the uncertainty around universal vaccine availability, remain major concerns. We therefore propose the establishment of an international candidate vaccine pool repository for potential respiratory diseases, supported by multiple stakeholders and countries that contribute facilities, technologies, and other medical and financial resources. The types and categories of candidate vaccines can be determined based on information from previous pandemics and epidemics. Each participant country or region can focus on developing one or a few vaccine types or categories, together covering most if not all possible potential infectious diseases. The safety of these vaccines can be tested using animal models. Information for effective candidates that can be potentially applied to humans will then be shared across all participants. When a new pandemic arises, these pre-selected and tested vaccines can be quickly tested in RCTs for human populations.

Community health workers in clinical research at the example of a phase IIIb/ IV antimalarial drug trial conducted in five African countries.

Global health, particularly in underserved settings can benefit immensely from well-trained community health workers (CHWs) supporting primary healthcare interventions. They can reduce morbidity and mortality of infectious diseases like malaria. Disease control programs can particularly benefit from a tight link between CHWs and communities and several studies have shown the benefit of the participation of non-facility-based CHWs in malaria control program activities for reducing malaria-related mortality in children. Because CHWs are often part of and trusted by served communities, they can also be an important resource to address challenges faced by their communities. Where post-marketing surveillance systems are underserved, they can relay important information about suspected safety signals and factors affecting therapeutic effectiveness in their communities. The CANTAM-Pyramax® trial was a phase IIIb/ IV cohort event monitoring study conducted at six centers in five African countries. To assess real-world effectiveness and safety of the anti-malarial pyronaridine-artesunate in 8560 malaria episodes, follow-up was not primarily conducted by medical staff but by specifically trained CHWs. This perspective paper discusses how the participation of a CHW workforce can be of benefit for effectiveness trials in limited-resource settings, using the example of the CANTAM-Pyramax trial.

Antibody responses to recombinant vesicular stomatitis virus-Zaire Ebolavirus vaccination for Ebola virus disease across doses and continents: 5-year durability.

OBJECTIVES: To report 5-year persistence and avidity of antibodies produced by the live-attenuated recombinant vesicular stomatitis virus (rVSV) expressing the Zaire Ebolavirus (ZEBOV) glycoprotein (GP), known as rVSV-ZEBOV (Ervebo®). METHODS: Healthy adults vaccinated with 300,000 or 10-50 million plaque-forming units of rVSV-ZEBOV in the WHO-coordinated trials of 2014-2015 were followed for up to 4 (Lambaréné, Gabon) and 5 (Geneva, Switzerland) years. We report seropositivity rates, geometric mean titres (GMTs), and population distribution of ZEBOV-GP ELISA IgG antibodies, neutralizing antibodies (pseudovirus and live-virus neutralization) and antibody avidity; the primary outcome was ZEBOV-GP ELISA IgG GMTs at 4 or 5 years compared with 1 year (Y1) after immunization. RESULTS: Among the 168 eligible vaccinees (Geneva: 97 and Lambaréné: 71) enrolled 1 year post-immunization, 146 (87%) remained enrolled at 4 years (Geneva: n = 88, Lambaréné: n = 58), and 84 (87%, Geneva) at 5 years post-vaccination. ZEBOV-GP ELISA IgG GMTs plateaued, with no declining trend from 1 year through the last time point assessed (1147.8 [95% CI 874.3-1507.0] at Y1 versus 1548.1 [95% CI 1136.6-2108.5] at Y5 in Geneva volunteers receiving ≥10 million plaque-forming units of rVSV-ZEBOV), their avidity matching that of ZEBOV convalescents. Live-virus neutralizing antibodies were detected for shorter periods and in fewer vaccinees (53/95 [56%] at Y1 versus 35/84 [42%] at Y5 in Geneva volunteers, all dose levels). DISCUSSION: Titres at Y1 emerged as a correlate of antibody persistence at Y5. The findings of persistent ZEBOV-GP ELISA IgG titres yet shorter-lasting, lower titres of live-virus neutralizing antibodies suggest the contribution of antibody-mediated protective mechanisms other than neutralization. Long-term clinical efficacy of rVSV-ZEBOV, however, requires further study.